I'm sorry to hear what you're experiencing, that sucks. It's hard to comprehend when you're given a diagnosis for a medical condition that has no cure, can't always be treated successfully, and is a lifetime sentence basically.
In my case, I've been dealing with osteoarthritis for over 20 years, and neuropathy in my feet for 10 years now, and it can be overwhelming at times.
If there's any way you can see your grandson on his birthday, do it, whatever pain or inconvenience it may cause, it'll be worth it in the end. Our grandkids are one of the few reasons I'm still here dealing with all this crap everyday.
All you can do is take it one day at a time.